Surface amination of poly(acrylonitrile)

The surface amination of poly (acrylonitrile) by ammonia plasma treatment has been studied. Furthermore, two other surface modification techniques have been investigated, the plasma chemical decomposition of an amino group containing chemical (tris-(2-aminoethyl)amine) onto the polymer surface and the surface reduction by lithium aluminium hydride. The three different methods are compared with respect to the adhesion improvement of the coatings onto the modified surfaces

Reactions with 1.3 propane sultone for the synthesis of cation-exchange membranes

For several reasons it is interesting for membrane technology to introduce strongly anionic groups in membranes. Therefore the possibilities of 1.3 propane sultone were studied to modify cellulose, cellulose acetate and polyacrylonitrile.\ud \ud The results showed that cellulose and cellulose acetate could be modified by a direct reaction of 1.3 propane sultone with the available hydroxyl groups. The nitrile groups in polyacrylonitrile had to be reacted first with hydrogen sulphide to give reactive thioamide groups, able to react with the sultone. These results give evidence for 1.3 propane sultone being a useful chemical for modification of polymers, its carcinogenic properties will however prevent application

Uptake of tridodecylmethylammonium chloride by PVC

The uptake of tridodecylmethylammonium chloride (TDMAC) by poly(vinyl chloride) has been investigated to provide a more quantitative basis for the preparation of blood-compatible surfaces based on TDMAC-heparin coatings. Sorption isotherms of TDMAC from toluene-cyclohexane and toluene-methanol mixtures have been measured. In toluene-cyclohexane mixtures, the TDMAC uptake is proportional to the degree of swelling of the polymer. From ion-exchange experiments with 36Cl-, it appears that only a small fraction of the TDMAC remains near the PVC surface to provide the heparin binding capacity. Methanol forms a strong H-bonded complex with TDMAC in toluence and prevents its sorption by PVC

High-performance liquid chromatography as a technique to measure the competitive adsorption of plasma proteins onto latices

Isotherms of human serum albumin (HSA), human immunoglobulin G (HIgG), and human fibrinogen (HFb) onto a polystyrene (PS)-latex were determined by depletion of protein in the solution, which was either followed by radioactivity measurements or by UV spectroscopy. Different adsorption isotherms for the same protein were obtained when either radioactivity measurements or UV spectroscopy was used as a detection technique. In order to obtain reliable results from competitive protein adsorption experiments, a method based on the use of high-performance liquid chromatography was developed. A strong preferential adsorption of HFb was observed when adsorption studies were carried out with mixtures of HSA, HFb, and HIgG. When adsorption studies were carried out with solutions containing HSA monomer and dimer, a strong preferential adsorption of HSA dimer was also observed

Characterization of hemodialysis membranes by inverse size exclusion chromatography

Inverse size exclusion chromatography (i-SEC) was used to characterize three different cellulosic hollow fiber hemodialysis membranes, i.e. low-flux cuprophan and hemophan and high-flux RC-HP400A. With the i-SEC technique the pore size distribution and porosity of a membrane can be determined and adsorption phenomena can be studied. The membranes showed clear differences in pore size and porosity, the high-flux RC-HP400A membrane has a larger pore size as well as a higher porosity. For all the membranes it was found that the elution curves were best described by a homoporous pore volume distribution. It appeared that the bound or non-freezing water in the membranes was at least partly accessible to solutes. The test molecules creatinine and vitamin B 12 both adsorbed to the cellulosic membranes. The adsorption behavior of creatinine was strongly dependent on the NaCl concentration present. The observations could be explained by assuming that cuprophan and RC-HP400A are negatively charged whereas hemophan is positively charged due to the modification with N,N-diethylaminoethyl ether. The net charge of the hemophan is smaller

The feasibility of radiolabeling for human serum albumin (HSA) adsorption studies

Human serum albumin (HSA) was labeled in various ways and with different radioactive labels (Technetium-99m and Iodine-125). Characterization with electrophoresis on polyacryl gel and immunoelectrophoresis did not reveal differences between labeled and nonlabeled HSA. The release of the label from labeled proteins in phosphate buffer (pH 7.4) was studied as a function of time. 125I-labeled proteins were stable and 99mTc-labeled proteins showed different stabilities depending on the labeling method which was used. The adsorption behavior of labeled HSA and HSA onto polystyrene (PS) and silicon rubber (SR) was studied by using two methods. It appeared that all labeled HSA compounds showed a preferential adsorption onto PS (and SR) substrates. The 99mTc-labeled HSA showed a high value of the preferential adsorption factor (φ 1). The φ value for 125I-labeled HSA was about 1.4. It was also shown that φ was dependent on the kind of substrate used. The methods developed to determine preferential adsorption of labeled proteins compared to their nonlabeled analogs are also generally applicable for different types of compounds

LC-MS proteomics analysis of the iInsulin/IGF-1-deficient Caenorhabditis elegans daf-2(e1370) mutant reveals extensive restructuring of intermediary metabolism

The insulin/IGF-1 receptor is a major known determinant of dauer formation, stress resistance, longevity, and metabolism in Caenorhabditis elegans. In the past, whole-genome transcript profiling was used extensively to study differential gene expression in response to reduced insulin/IGF-1 signaling, including the expression levels of metabolism-associated genes. Taking advantage of the recent developments in quantitative liquid chromatography mass spectrometry (LC-MS)-based proteomics, we profiled the proteomic changes that occur in response to activation of the DAF-16 transcription factor in the germline-less glp-4(bn2);daf-2(e1370) receptor mutant. Strikingly, the daf-2 profile suggests extensive reorganization of intermediary metabolism, characterized by the upregulation of many core intermediary metabolic pathways. These include glycolysis/gluconeogenesis, glycogenesis, pentose phosphate cycle, citric acid cycle, glyoxylate shunt, fatty acid beta-oxidation, one-carbon metabolism, propionate and tyrosine catabolism, and complexes I, II, III, and V of the electron transport chain. Interestingly, we found simultaneous activation of reciprocally regulated metabolic pathways, which is indicative of spatiotemporal coordination of energy metabolism and/or extensive post-translational regulation of these enzymes. This restructuring of daf-2 metabolism is reminiscent to that of hypometabolic dauers, allowing the efficient and economical utilization of internal nutrient reserves and possibly also shunting metabolites through alternative energy-generating pathways to sustain longevity

Predicting flux decline of reverse osmosis membranes

A mathematical model predicting flux decline of reverse osmosis membranes due to colloidal fouling has been verified. This mathema- tical model is based on the theory of cake or gel filtration and the Modified Fouling Index (MFI). Research was conducted using artificial colloidal solutions and a pilot plant equipped with ultrafiltration membranes. Polystyrene latex spheres, having a size of about 0.05-0.08 μm were used as a foulant.\ud \ud The result of this research was, that the measured and calculated values of flux decline of the ultrafiltration membranes as a function of time agree reasonably well. The difference between the measured and calculated values may be explained by the assumption, that initially blocking filtration occurs instead of cake or gel filtratio